Apparatus and methods for monitoring water consumption and filter usage

ABSTRACT

Apparatus and methods for employing electrical properties of water to indicate the level of filtered water in a filtered water container. The container is fitted with a hopper that holds unfiltered water. The hopper is fitted at its base with a removable and replaceable filter cartridge. Water is filtered by draining through the filter medium contained in the filter cartridge into the lower portion of the container. The water level in the lower portion of the container is monitored by means of one or more water level detector strips in the lower portion of the container. The detector strips are in electrical communication with a detection circuit and a control unit. The control unit uses the detection strips to monitor water level and uses such data to track filtered water consumption and to determine when the filter cartridge should be replaced.

FIELD OF THE INVENTION

The present invention relates to an improved apparatus and method fordetermining filtered water consumption and usage of a filter cartridgeby monitoring the water level in a filtered water container.

BACKGROUND OF THE INVENTION

The quality of drinking water varies widely according to the amount ofpollutants in the water source. Home water treatment using replaceablefilter cartridges fitted in a filtered water container is a popularmethod to improve drinking water quality. Within a filter cartridge is afilter medium comprising substances and chemical compounds capable ofdecreasing the concentration of heavy metals such as copper, cadmium,zinc, aluminum, mercury and free chlorine. Some filter media are alsocapable of limiting the growth of certain microorganisms. It is knownthat the performance of the filter medium decreases with usage. Thus, afilter cartridge should be replaced after a known amount of water hasfiltered through it.

There exist mechanical and electronic mechanisms built into filteredwater containers to alert the user of the need to replace the filtercartridge. All such methods and devices suffer from drawbacks.

One group of inventions merely shows the time elapsed from cartridgereplacement as the method to indicate cartridge usage. Inventions suchas those disclosed in U.S. Pat. Nos. 4,895,648 and 5,665,224 employ amechanical date indicator to allow a user to record the date ofinsertion of a new filter cartridge. Such date indicators are intendedto remind users to replace the cartridge after a given amount of timehas elapsed. Such reminders are not always reliably adhered to. Anelectronic version of such a device was disclosed in U.S. Pat. No.6,224,751 B1. In the device, an electronic time counter activated by apush button starts the counting. The indication of the status ofcartridge usage is dependent on time elapsed from pushing thestart-button. The use of the time-elapse method in calculating cartridgeusage is only reliable to the extent that the estimated usageapproximates the actual usage. In reality, the usage of the filtercartridge can vary tremendously from the time elapsed since itsinsertion. Another drawback of the time-elapse method is its reliance onthe user to activate the time counting by resetting the date indicatoror the electronic time counter, the omission of which renders the methoduseless.

Another group of inventions are mechanisms built into or around the lidof the filtered water container, which counts the number of times thatthe lid is opened for water filling. In EP 0,861,809A1 and WO 95/29131,the lid includes a closure plate through which unfiltered water ispoured into the filtered water container. The opening and closingmovements of the closure plate trigger a mechanical mechanism thatadvances a rotatable member bearing an indicator, which purportedlyindicates the state of usage of the cartridge. U.S. Pat. No. 4,986,901disclosed a filter bottle cap fitted with a mechanism that advances acounter each time the cap is accessed for water filling.

In WO 96/13318, U.S. Pat. No. 5,900,138 and WO 00/66245, the number oftimes that the lid of the filtered water container is opened is alsocounted by mechanical, electronic or electromagnetic means. The devicesdisclosed in these references are based on the assumption that each timethe trigger mechanisms are activated, a theoretically constant amount ofwater is filled into the filtered water container. However, such anassumption does not account for errors in counting such as when thetrigger mechanism is inadvertently manipulated, accessed during cleaningor amounts of water that are less than the actual capacity of reservoirare used.

There also exist references that rely on flow meters to detect theamount of water that has passed through a filtration device for theindication of water filter cartridge usage. For example, U.S. Pat. No.4,772,386 discloses a water filter cartridge attached to a housinghaving an impeller driven by water flow. The impeller is connected to arotating toothed disc, which abrades and cuts a trigger wire after anestimated amount of water has flowed through the impeller. The cuttingof the trigger wire shuts off the water flow. U.S. Pat. Nos. 4,681,677,6,024,867 as well as WO 03/028848 A1 describe flow meters attached tofiltration devices. In particular, U.S. Pat. No. 4,681,677 describes theuse of a flow meter for monitoring water flowing into a water treatmentprocessor. U.S. Pat. No. 6,024,86 describes the use of the movement of aball in a water flow channel in order to detect the amount of filteredwater flow. WO 03/028848 A1 describes a flow meter fitted to the lid ofa filtered water container. The flow meter consists of a turbine wheel,which is rotated by the passage of unfiltered water. The trigger wiremethod disclosed in U.S. Pat. No. 4,772,386 is imprecise because thecutting efficiency of the toothed disc deteriorates over time and theabrasive resistance of each trigger wire can vary. As with mechanicalcounting mechanisms described earlier, flow meters can suffer frommechanical breakdown with wear and tear. For the flow meter described inWO 03/028848 A1, in particular, the flow meter can be inadvertentlyactivated during movement of the lid or the filtered water containerinadvertently or necessarily.

Other methods of indicating the exhaustion of a filter cartridge rely onthe blockage of water flow within the cartridge. U.S. Pat. No. 3,038,610uses a filter medium that swells upon its exhaustion to block waterflow. U.S. Pat. No. 6,428,687 employs a synthetic material to blockwater flow. These methods, however, only indicate the duration of timethat the filter medium has contacted water.

There is accordingly a need for a more accurate and robust method anddevice for measuring filter usage in a filtered water container.

SUMMARY OF THE INVENTION

The present invention determines filter usage by using amicroprocessor-controlled sensor to detect and monitor changes in thelevel of filtered water in a filtered water container. Further, thepresent invention provides the additional advantages of monitoringfiltered water consumption and current water level within the filteredwater container.

One aspect of the present invention provides a water level sensor formeasuring a water level of a filtered water container. The water levelsensor comprises a detection circuit and a detection sensor. Thedetection sensor is in electrical communication with the detectioncircuit. The detection sensor comprises a first electrode pair having afirst and second electrode. The first and second electrodes are extendedalong a length of the filtered water container. The first and secondelectrodes are spaced sufficiently far apart from each other that achange in an electrical property associated with the first and secondelectrode, caused by the change in the water level in the filtered watercontainer, is detectable by the detection circuit. In some instances,the electrical property associated with the first electrode and thesecond electrode is one or more of (i) a change in a resistance acrossthe first and second electrode, a change in a capacitance between thefirst and second electrode, a change in a voltage across the first andsecond electrode, and a change in a current across the first and secondelectrode.

In some embodiments, the water level sensor has a control unit that isin electrical communication with the detection circuit. The control unitis programmed to use the detection circuit and the detection sensor totrack the change in water level in the filtered water container and tomonitor a status of a water filter in the filtered water container.

In some embodiments, the filtered water container further comprises aswitch that is in electrical communication with the detection circuit.This switch is positioned in the filtered water container so that, whenthe switch is in a first state, the control unit determines that thefiltered water container is in a nonfunctional state, and, when theswitch is in a second state, the control unit determines that thefiltered water container is in a functional state. In such embodiments,the control unit uses an electronic reading from the detection circuitto determine the water level of the filtered water container when thefiltered water container is in the functional state. Furthermore, thecontrol unit does not use an electronic reading from the detectioncircuit to determine the water level of the filtered water containerwhen the filtered water container is in the nonfunctional state.

In some embodiments, the switch is toggled between the first and secondstate by a user. In some embodiments, the switch is positioned withinthe filtered water container so that the switch is in the first statewhen a lid of the filtered water container is open or removed from thefiltered water container and the switch is in the second state when thelid is closed or attached to the filtered water container. In someembodiments, the switch is a bubble level switch that includes a firstbubble sensor electrode and a second bubble sensor electrode in anenclosure trapping (i) a fluid and (ii) a bubble. In such embodiments,the bubble sensor electrode is in the first state when the bubblecontacts the first bubble sensor electrode or the second bubble sensorelectrode and the bubble sensor electrode is in the second state whenthe bubble does not contact the first bubble sensor electrode or thesecond bubble sensor electrode.

In some embodiments, the control unit determines that the filtered watercontainer is in a functional state when a rate of change in a waterlevel in the filtered water tank is below a predetermined rate and thecontrol unit determines that the filtered water container is in anonfunctional state when a rate of change in a water level in thefiltered water tank is above a predetermined rate. In some embodiments,the water filter container is fitted with a hopper that holds unfilteredwater. The hopper is fitted at its base with a removable and replaceablefilter cartridge so that water is filtered by draining through a filtermedium contained in the filter cartridge into a lower portion of thewater filter container.

Another aspect of the invention provides a water level sensor formeasuring a water level of a filtered water container. The water levelsensor comprises a detection circuit and a detection sensor. Thedetection sensor is in electrical communication with the detectioncircuit. The detection sensor comprises a sensor strip that is extendedalong a length of the filtered water container. The sensor strip housesa plurality of electrode pairs. Each electrode pair in the plurality ofelectrode pairs comprises a first and second electrode. Each electrodepair in the plurality of electrode pairs is in electrical communicationwith the detection circuit. The first electrode and the second electrodein an electrode pair in the plurality of electrode pairs are spacedsufficiently far apart from each other on the sensor strip so that achange in an electrical property associated with the first and secondelectrode, caused by the change in the water level in the filtered watercontainer, is detectable by the detection circuit.

In some embodiments, the electrical property associated with the firstelectrode and second electrode is one or more of a change in aresistance across the first electrode and the second electrode, a changein a capacitance between the first electrode and the second electrode, achange in a voltage across the first electrode and the second electrode,and a change in a current across the first electrode and the secondelectrode. In some embodiments, the plurality of electrode pairscomprises between 2 electrode pairs and 10 electrode pairs. In someembodiments, the plurality of electrode pairs comprises more than 10electrode pairs.

In some embodiments, the water level has a control unit that is inelectrical communication with the detection circuit. The control unit isprogrammed to use the detection circuit and the detection sensor totrack the change in water level in the filtered water container and tomonitor a status of a water filter that is in the filtered watercontainer.

In some embodiments, the detecting circuit includes a first lead (a), asecond lead (b) and a third lead (c). The first lead (a) is inelectrical communication with the first electrode in an electrode pairin the plurality of electrodes. The second lead (b) is in electricalcommunication with the second electrode in an electrode pair in theplurality of electrodes. The third lead (c) and the second lead (b) arein electrical communication across a resistor. The control unit isprogrammed to set the third lead (c) to a high voltage and the firstlead (a) a low voltage each time a first voltage drop is measured at thesecond lead (b). The control unit is further programmed to set the thirdlead (c) to a low voltage and the first lead (a) to a high voltage eachtime a second voltage drop is measured at the second lead (b). In someembodiments, control unit is programmed to switch to a low powerconsumption idle state when the second lead (b) is in a high voltagestate and to a high power consumption state when the second lead (b)drops from a high voltage state to a low voltage state.

Another embodiment of the present invention provides a method ofmeasuring a water level of a filtered water container. The methodcomprises detecting an electrical property associated with a firstelectrode and a second electrode in an electrode pair. The firstelectrode and the second electrode are extended along a length of thefiltered water container. The electrical property associated with thefirst electrode and the second electrode changes with changes in thewater level in the filtered water container. A change in the electricalproperty is determined, thereby allowing for measurement of the waterlevel of the filtered water container. In some embodiments, theelectrical property associated with the first electrode and the secondelectrode is one or more of a resistance across the first electrode andthe second electrode, a change in a capacitance between the firstelectrode and the second electrode, a voltage across the first electrodeand the second electrode, and a current across the first electrode andthe second electrode. In some embodiments, the method further comprisesusing the change in the electrical property to track a status of a waterfilter in the filtered water container.

The present invention thus provides an accurate and robust method andapparatus for indicating water cartridge usage or exhaustion in afiltered water container. It also omits the use of mechanical devicessuch as flow meters or those that are connected to the lid foropening/closing or access, whose effectiveness can deteriorate with wearand tear.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional objects and features of the invention will be more readilyapparent from the following detailed description and appended claimswhen taken in conjunction with the drawings, in which:

FIG. 1 is an illustration of a filtered water container according to thepresent invention;

FIGS. 2A and 2B are isolated views of a water level sensor within thefiltered water container of FIG. 1;

FIG. 3 is a cutaway view of a handle of the filtered water container ofFIG. 1, showing an electronic control system according to the presentinvention;

FIG. 4A is a functional block diagram of a water level monitoring systemaccording to the present invention;

FIG. 4B is a functional block diagram of an alternative water levelmonitoring system according to the present invention;

FIG. 5 is a schematic diagram of a detection circuit according to thepresent invention;

FIG. 6A is an illustration of an alternative embodiment of a water levelsensor according to the present invention;

FIG. 6B is a close-up view of the water level sensor of FIG. 6A;

FIG. 6C is a cross-sectional view of the water level sensor of FIG. 6B,taken along line 6C—6C;

FIG. 7 is functional block diagram of a water level monitoring systemincorporating the water level sensor of FIGS. 6A–C;

FIG. 8 is a is functional block diagram depicting a voltage dividerdetection circuit within the water level monitoring system of FIG. 7;

FIG. 9 is a timing chart depicting the operation of the voltage dividingcircuit of FIG. 8;

FIG. 10 is another embodiment of a water level sensor according to thepresent invention;

FIG. 11 is still another embodiment of a water level sensor according tothe present invention;

FIG. 12 is yet another embodiment of a water level sensor according tothe present invention;

FIG. 13 is an illustration of an alternative embodiment of the filteredwater container according to the present invention; and

FIG. 14 is a schematic diagram of a bubble switch according to thepresent invention.

Like reference numerals refer to corresponding parts throughout theseveral views of the drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Overview of theFiltered Water Container

FIG. 1 depicts a filtered water container 10 according to the presentinvention for providing filtered drinking water while monitoring waterlevel and determining filter cartridge usage. Container 10 has a mainbody 12, or vessel, preferably dimensioned as a beverage pitcher, andincludes at least three removable parts: a lid 14, a hopper 24 and awater filter cartridge 22. Hopper 24 is configured and dimensioned tofit within and engage with the upper portion of body 12 near lid 14 suchthat the bottom of hopper 24 and the base 18 of body 12 form a cavity 26within which filtered water is stored. Filter cartridge 22 is areplaceable filter cartridge and is dimensioned to be removably securedwithin an opening (not shown) in the bottom of hopper 24, such that aportion of filter cartridge 22 extends into cavity 26. Container 10 alsoincludes a handle 30 attached to or integral with one side of body 12.On an opposite side of body 12, cavity 25 extends past hopper 24 to forma spout to allow the pouring of filtered water from cavity 25 withoutremoval of hopper 24.

In typical use, a new filter cartridge 22 is secured within hopper 24and unfiltered water is poured through opening 16 and into hopper 24.Hopper 24 temporarily stores water until it flows through filtercartridge 22. Water flows under the force of gravity from hopper 24through filter cartridge 22, which includes a filter medium for removingimpurities in water. The effectiveness of the filter medium has atendency to decrease with usage over time. After passing through filtercartridge 22, the filtered water falls into cavity 26 where it is storedfor later consumption or use. To remove filtered water, a user cansimply grasp handle 30 and tilt container 10 to pour the water out ofspout 25. Lid 14 optionally includes a spout opening (not shown) tofacilitate pouring without removal of lid 14.

The basic configuration of container 10 described thus far is similar toexisting containers, for example the Terraillon Aqua 30 and Aqua 40(Terraillon, BP 73, 78403 Chatou cedex, France). Body 12, lid 14, andhopper 24 are preferably made of plastic (e.g., high-densitypolyethylene) or any other suitable materials known and used in the art.Filter cartridge 22 can be any suitable water filter cartridge designedor selected to fit within hopper 20. One skilled in the art willappreciate that above-described configuration and features of main body12, lid 14, hopper 24, and filter cartridge 22 are used for illustrativepurposes only, and can be modified without departing from the scope ofthe present invention.

Water Level Detection and Monitoring System

Referring again to FIG. 1, container 10 includes a unique water leveldetection and monitoring system 50 comprised of a water level sensor 40and an electronic control system 52. Water level sensor 40, also hereinreferred to as a detection sensor or a detector strip, preferably has anelongated shape and is disposed within cavity 26 along an inner wall ofbody 12. Sensor 40 is preferably oriented vertically and approximatelyspans the height of cavity 26 between base 18 and bottom of hopper 24such that, when filtered water is in cavity 26, a lower portion ofsensor 40 is below water level 27 and is in contact with water and anupper portion of sensor 40 is above water level 27 and is in contactwith air. Water level sensor 40 is in electrical communication withcontrol system 52 through wire 48. Wire 48 is disposed within handle 30as illustrated in FIG. 1

As shown in FIGS. 2A and 2B, one embodiment of water level sensor 40comprises an elongated pair 42 of parallel electrodes 42 a and 42 battached to a substrate 46. Electrodes 42 a and 42 b are electricallyconducting leads that are separated but positioned in close proximity toone another. Electrode pair 42 extends from the surface of substrate 46such that, when cavity 26 is filled with water, the portion ofelectrodes 42 a and 42 b below water line 27 are in contact with andseparated by water, such that the resistance or capacitance betweenelectrodes 42 a and 42 b varies as a function of water level 27.

Electrodes 42 a and 42 b can be made of any metallic or non-metallicelectrically conducting materials. Preferably, corrosion resistantmaterials such as chromed-alloy, stainless steel, CoCr, NiCr,semi-precious alloy, titanium alloy, and the like are utilized. In oneembodiment, electrodes 42 a and 42 b are covered with a metallic platingsuch as gold or platinum to help prevent corrosion. Electrode materialsare preferably non-toxic. Substrate 46 is preferably constructed ofplastic (e.g., high-density polyethylene, low-density polyethylene,polypropylene, cellulose acetate, rigid vinyl, plasticized vinyl,cellulose acetate butyrate, nylon, polymethylmethacrylate, polystyrene,or acrylonitrile butadiene-styrene), ceramics (e.g., silicate ceramics,glass ceramics) or any other relatively non-conducting material, and canbe adhered to or imbedded within interior wall of container body 12. Insome embodiments, substrate 46 is simply the wall of body 12. Electrodes42 a and 42 b are respectively connected to leads 43 a and 43 b. Leads43 a and 43 b conduct electrical currents to and from control system 52.Leads 43 a and 43 b are insulated from one another, and can be bundledtogether as a single wire 28.

Referring to FIG. 3, control system 52 includes a control unit 80,detection circuit 70 and a display 60. Control unit 80 is preferably ageneral purpose microprocessor that communicates with sensor 40,detection circuit 70 and display 60 to provide overall operation andcontrol of water level detection and of monitoring system 50.Alternatively, control unit is an application specific integratedcircuit (ASIC) or any other form of processing means. Detection circuit70 includes one or more of a resistance circuit, a capacitance circuit,an operational amplifier, and/or other means of determining changes inresistance or capacitance between electrode pair 42 and forcommunicating such change to control unit 80. A battery 66 or otherpower source provides power for control system 52 and is held within abattery compartment 64 by a battery cover 68. An optional mode button 62communicates with control unit 80 and allows a user to select betweendifferent functions or to display different parameters, such as currentwater level, total water usage or consumption, elapsed time since lastfilter change, or remaining filter life measured in terms of any of avariety of metrics such as time remaining, remaining amount of waterthat can be filtered, or number of fills remaining.

Display 60 is preferably a liquid crystal display (LCD), but otherdisplays or status indicators are within the scope of the presentinvention. Such alternative arrangements include light emitting diode(LED) or analog displays, or one or more indicator lights that changestate, intensity or color to indicate parameters such as water level,total water consumption, or filter life. Control unit 52 preferably hasan integrated memory for storing information such as operationalparameters, water level data, instructions, component states, and thelike. However, system 50 can also incorporate additional memory inaddition to or instead of integrated microprocessor memory. Suchadditional memory can be read only memory (ROM) and/or random accessmemory (RAM) that is in electrical communication with microprocessor 80.

Operation of Water Level Detection and Monitoring System

FIGS. 4A and 4B are functional diagrams illustrating two embodiments ofthe operation of water level detection and monitoring system 50. In bothcases, system 50 includes detection sensor 40, detection circuit 70,control unit 80, and display unit 60 as shown and described above. Inboth embodiments, detection sensor 40 is as shown in FIGS. 2A and 2B,including a pair of parallel electrode plates 42 a and 42 b. Adifference between the two approaches lies in the circuit 72, 74 used indetection circuit 70 and whether such circuit 72, 74 is configured todetect changes in resistance across electrodes 42 a and 42 b (FIG. 4A)or capacitance between electrodes 42 a and 42 b (FIG. 4B).

Because the resistance of water differs from the resistance of air, theresistance measured across electrode plates 42 a and 42 b (FIG. 4A)varies as a function of water level 27. Further, because the capacitanceof water differs from the capacitance of air, the capacity betweenelectrode plates 42 a and 42 b (FIG. 4B) also varies as a function ofwater level 27.

Referring to FIG. 4A, resistance across electrode plates 42 (42 a and 42b) is proportional to the amount of contact area between the twoelectrode plates that is exposed to air when electrode plates 42complete a direct current (DC) circuit. This is because the electricalresistance of air is much higher than the electrical resistance ofwater. Therefore, as air is replaced by water between the two electrodes42, the voltage across electrode plates 42 decreases.

Referring to FIG. 4B, electrical capacitance across electrode plates 42is proportional to the amount of contact area between the two electrodeplates that is exposed to water when plates 42 complete an alternatingcurrent (AC) circuit. This is because the dielectric constant of wateris about 80 whereas the dielectric constant of air is about 1. Sincevoltage across plates 42 is given by the equation:

${\frac{\mathbb{d}}{\mathbb{d}T}\left( {V_{42a} - V_{42b}} \right)} = \left( \frac{I_{{42A}\rightarrow{42B}}}{C} \right)$where C is the dielectric constant between plates 42, increasing waterwill cause the magnitude of voltage to decrease when leads 42 completean AC circuit.

Accordingly, in both embodiments (FIGS. 4A and 4B), when the contactarea of electrode pair 42 increases as filtered water level 27 rises,the voltage across the circuits depicted in FIGS. 4A and 4B drop.Detection circuit 70 detects this drop in voltage and communicates acorresponding signal to microprocessor control unit 80. Microprocessorcontrol unit 80 receives the signal from detection circuit 70 andperiodically does one or more of the following: (1) maintains a recordof the current water level and/or the change in the water level, (2)calculates the amount of water consumption by monitoring the amount ofwater that was poured out of the lower portion of container 10, (3)calculates the amount of water filtration by monitoring the amount ofwater that was filtered into the lower portion of the container, and/or(4) calculates the status of usage of the water filter cartridge bymonitoring water consumption and water filtration since the lastcartridge replacement. Information regarding any of these measured orcalculated parameters can be displayed to a user on display unit 60.Accordingly, some embodiments of the present invention provide a display60 in electrical communication with a control unit 80, wherein thecontrol unit 80 is capable of causing the display 60 to displayinformation derived from a current water level or a change in currentwater level in filtered water container 10. In some embodiments, suchinformation includes one or more of a water level of the filtered waterlevel container 10, a status of a water filter cartridge (water filter)22 that is disposed within the filtered water container 10, adetermination of whether the filtered water container 10 is in afunctional state, a determination of whether the filtered watercontainer is in a nonfunctional state, a time elapsed or an amount offiltered water consumed since a last filter cartridge change. Thedisplay 60 can also display information such as a current time, awarning of overfilling, and a reminder to refill.

It should be noted that the distinct modules of FIGS. 4A and 4B areshown for the purpose of illustration only, and some of the shownmodules can be combined into a single physical device with no loss ofgenerality.

Water Level Detection Using Resistance Principles

In one embodiment, circuit 72 of FIG. 4A can be described by the circuitillustrated in FIG. 5. A predetermined direct current (DC) voltage V isapplied to electrode 43 a as determined by control unit 80. Electrode 43b is attached to ground. The resistivity of air is considerably higherthan the resistivity of water. Thus, the resistivity R of FIG. 5 willvary as a function of water lever. Because resistivity R of circuit 72varies as a function of water level 27, an increase in water level willresult in a decrease in the resistitivity across leads 42 a and 42 b.The decrease in resistivity will result in a decrease in voltage. Thisvoltage change is detected by microprocessor control unit 80. Thus,microprocessor 80 uses output voltage Va to calculate water level 27 atany given time.

Water Level Detection Using Capacitance Principles

The example circuit described above with respect of FIG. 5 exploits thedifference in the resistance of water and air. However, as shown in FIG.4B, the detection circuit 70 of the present invention can be configuredto detect changes in capacitance between electrodes 42 a and 42 b in analternating current (AC) circuit. In such instances, the two electrodes42 a and 42 b comprise the two plates of a capacitor, such that when anelectric charge Q is applied to one plate 42 a of the capacitor, anopposite charge −Q appears on the other plate 42 b. The presence of thischarge gives rise to a voltage V across the capacitor. This voltage islinearly proportional to the stored charge, according to the equationQ=CV. The quantity C is a constant, usually expressed in picoFarads,known as the capacitance, whose value depends upon the physicalstructure of the capacitor.

The physical parameters of the “capacitor” that affect C include theeffective surface area A of the plates 42 a and 42 b, the distance Dbetween plates 42 a and 42 b, and the dielectric constant K of thematerial between plates 42 a and 42 b. These parameters are related bythe equation:C≈K(A/D)The dielectric constant is a numerical value on a scale of 1 to 100 thatrelates to the ability of the dielectric material to store anelectrostatic charge. In the instant case, the dielectric materialbetween electrode plates 42 a and 42 b is either air or water, or somecombination thereof. The dielectric constant K of air is 1 and thedielectric constant of water is approximately 80. Here, the distance Dbetween electrode plates 42 a and 42 b is constant, so the capacitance Cof the system is a function of amount of effective surface area betweenelectrodes 42 a and 42 b that are in contact with, and thereforeseparated by, water:C≈(1×A _(air))+(80×A _(water))As water level increases, the total capacitance output of the systemincreases. Such changes in capacitance can be detected by a standardop-amp or capacitance detection circuit within detection circuit 70 incommunication with control unit 80, and this signal can be used by thecontrol unit to calculate and monitor water level 27.

Water Level Sensors Having an Array of Electrode Pairs

FIGS. 6–9 depict features and methods of use of an embodiment of thewater level detection and monitoring system 50 of filtered watercontainer 10 of FIG. 1, now utilizing a water level sensor 140 having anarray of electrode pairs. Referring to FIGS. 6A and 6B, one willrecognize that the basic features of sensor 140 are essentially the sameas sensor 40 of FIGS. 2A and 2B, except that sensor 140 includesmultiple electrode pairs, e.g. 142-1, 142-2, 142-N, rather than a singlepair 42 as described with respect to FIGS. 2A and 2B. In someembodiments, N is between 2 and 10. In some embodiments, N is 10 orgreater. In some embodiments N is between 10 and 1000. Each respectiveelectrode pair 142 is preferably oriented vertically with respect toneighboring electrode pairs as shown in FIGS. 6A and 6B, such that eachpair of electrodes 142 corresponds to a known water level 27. Electrodepairs 142 are attached to or imbedded within substrate 46.

In this embodiment, except for their respective positions along thevertical length of sensor 140, each electrode pair 142 has essentiallythe same features and characteristics. Each electrode pair 142 comprisestwo electrically-conducting electrode plates, e.g. 142 a-1 and 142 b-1,that extend from the surface of substrate 46 into the cavity ofcontainer 10. Electrodes 142 a and 142 b are substantially parallel andin close proximity to one another, but separated from one another byeither air (e.g., when water level 27 is below electrode pair 142) orwater (e.g., when water level 27 is above electrode pair 142).

Leads 145 a and 145 b connect electrodes 142 a and 142 b, respectively,to a detection circuit (e.g., circuit 170 of FIG. 7, described below).In this embodiment, for convenience of design, leads 145 a and 145 bfrom each electrode pair 142 is bundled into a lead bundle 154. Eachlead, e.g. 145 a-1 and 145 b-1 is insulated from all other leads suchthat current does not pass between them.

As described earlier, suitable electrode materials include conductingcorrosion resistant materials such as chromed-alloy, stainless steel,CoCr, NiCr, semi-precious alloy, titanium alloy, and the like. In oneembodiment, electrodes 142–190 are covered with a metallic plating suchas gold or platinum to help prevent corrosion. Electrode materials arepreferably non-toxic.

Operation of Water Level Sensors Having an Array of Electrode Pairs

Referring to the functional diagram of FIG. 7, each electrode pair 142of detection sensor 140 is connected to a corresponding circuit 172within detection circuit 170. Each detection circuit 172 communicateswith and is controlled by control unit 80 as described with respect toFIGS. 4A and 4B. Control unit 80 continuously, periodically or otherwisepolls electrode pairs 142 to obtain signals from detection circuitsindicating which electrodes are in contact with water and which are incontact with air. In a power-efficient embodiment described below, withreference to FIGS. 8 and 9, control unit 80 does not poll electrodes,but rather responds to changes in the voltage across the electrodes. Inother embodiments, control unit 80 ignores electrodes that are knownfrom previous measurements to be a predetermined distance above and/orbelow water line 27. Regardless of the polling or sampling method,control unit 80 uses output signals from circuits 172 to determinedesired parameters such as current water level, changes in water level,total amount of water filtered or consumed, remaining filter life, etc.

As with FIGS. 4A and 4B, filtered water level 27 is detected for eachelectrode pair 142 of FIG. 7 by its corresponding detection circuit 172measuring a change in voltage between each electrode pair, e.g. betweenelectrode pair 142 a-1 and 142 b-1. The voltage across those electrodepairs immersed in water will be determined by the properties of waterwhereas the voltage across those electrode pairs above the water levelwill be determined by the properties of air. Water level 27 is thencalculated as being at or slightly above the highest pair of electrodesexhibiting a voltage that is determined by that of water. In suchembodiments, there is no need for calibration of resistance orcapacitance measurements between a particular electrode pair bymicroprocessor 80, as microprocessor 80 simply determines whetherresistance (or alternatively capacitance) between a pair of electrodeplates, e.g. 142 a-1 and 142 b-1, is either high or low.

Resolution of the system is determined by the vertical length of theelectrode pairs, the number of electrode pairs, and vertical distancebetween neighboring electrode pairs, and, in some instances, how oftenthe electrodes are sampled. More electrode pairs, and/or smallervertical spaces between electrode pairs provides greater resolution. Inan alternative embodiment, the microprocessor resolves fine changes inwater level, e.g., within the span of one electrode pair, by calculatinggraded changes in resistance or capacitance between and electrode pairas a function of water level as described above with respect to FIGS.4A, 4B and 5.

Power-Efficient Water Level Detection Circuit

FIG. 8 illustrates an example of a power efficient detection circuitaccording to one embodiment of the present invention. One skilled in theart will appreciate that while only one electrode pair 142 (142-1) andcircuit 172 (172-1) is shown in FIG. 8, the following functionaldescription applies to each of the electrode pairs 142 and correspondingcircuits 172 shown in FIG. 7.

In this embodiment, circuit 172-1 is a voltage divider circuitcomprising three leads, 143 a-1, 143 b-1 and 143 c-1 that are alsorespectively referred to as leads “(a)”, “(b)” and “(c)”. As shown anddescribed above, lead 143 a-1 is electrically connected to electrode 142a-1 and lead 143 b-1 is electrically connected to electrode 142 b-1.Lead 143 c-1 is also electrically connected to electrode 142 b-1 throughresistor 176 (R₁). All three leads (a), (b) and (c) are in electricalcommunication with control unit 80, which provides control and inputsignals to and receives output signals from circuit 172-1. Optionally,level-setting adjusting circuit 194 is used to adjust signals cominginto or out of control unit 80. Such level-setting adjusting circuit 194is needed in some instances to reduce the range of voltages and currentsproduced by detection circuit 170 to the dynamic range of control unit80.

Circuit 172-1 is designed to communicate to control unit 80 changes inthe state of electrode pair 142-1, e.g., whether the electrode pair isin contact with water or not. As described above, the voltage across theelectrode pair is different when the pair is immersed in air as opposedto water. Conceptually, therefore, electrode pair 142-1 is shown anddescribed herein as a switch 142-1, where the switch has two possiblestates: open or closed. When water level reaches electrode pair 142-1,the presence of water between electrodes 142 a-1 and 142 b-1 reduces theresistance between these electrodes from a very large value thateffectively does not allow current to flow, to one that allows currentto flow. Thus, when water reaches electrode pair 142-1, the circuit 170is closed. Conversely, when the water level is below electrodes,relatively little or no current flows between electrodes 142 a-1 and 142b-1 and circuit 170 is open. When (a) is connected to a low voltage(e.g., a ground voltage) and (c) is connected to a high signal voltage,the voltage at (b) is determined by the voltage divider formula:

$V_{OUT} = {V_{IN}\left\lbrack \frac{R_{2}}{R_{1} + R_{2}} \right\rbrack}$where R₁ is the resistance resistor 176 and R₂ is the resistance acrossleads 142 a and 142 b.

FIG. 9 is a timing diagram illustrating typical operation of circuit 170of FIG. 8. In general, leads (a) and (c) carry input signals fromcontrol unit 80 and lead (b) conducts output signals to control unit 80.Although signals may be AC or DC signals of known values, signalsdelivered to the circuit via leads (a) and (c), and received from thecircuit via (b), will be described here as either low (“0”) or high(“1”). At an arbitrary starting time, to, water level is “Low” meaningthat air rather than water separates electrodes 142 a-1 and 142 b-1.Therefore, switch 142-1 is considered “open”. In this state, controlunit 80 has provided a high voltage to (c) and a low voltage to (a). Thehigh resistance properties of air dominate the voltage dividercircuitry, with a very high R₂. Thus, V_(IN) equals V_(OUT). As such,the output voltage at (b) is the same as V_(IN), which is considered alogical “high.” In this high output (b) state, control unit 80 remains“off”, or idle with respect to circuit 170. At time t1, the water levelis still low, the switch is still open, the voltage states of (a), (b)and (c) remain the same, and microprocessor 80 remains idle.

At time t2, water level increases and is high. This means thatelectrodes 142 a-1 and 142 b-1 are immersed in water. Now R₂ isdetermined by the resistive properties of water rather than air. V_(OUT)no longer equals V_(IN). For R₁ with suitably chosen values, V_(OUT)will be substantially less than that of V_(IN). As a result, there willbe a voltage drop at (b), shown now as in state “0”, or “low.” Thechange in lead (b) from the high voltage state to the low voltage statecauses microprocessor 80 to wake up (turn “on”). The fact that thevoltage at lead (b) has dropped from logical high to low means thatwater level 27 has surpassed the physical position of the correspondingleads 142 in the water tank and this fact is noted by microprocessor 80and stored in memory within the microprocessor or associated with themicroprocessor.

At a time t3, microprocessor 80 reverses voltage states of (a) and (c),such that terminal (a) is now at a high voltage and terminal (c) is nowat a low voltage. The reversal of the voltages at terminals (a) and (b)cause the voltage at terminal (b) to adopt the value V_(OUT), where

$V_{{OUT}^{\prime}} = {V_{IN}\left\lbrack \frac{R_{1}}{R_{2} + R_{1}} \right\rbrack}$Since R₂ remains small because sensor 142 is immersed in water, andsince R₁ is constant, the reversal of the voltage states at leads (a)and (c) immediately causes the voltage at terminal (b) to switch fromlow to high as noted at time t4 in FIG. 9. It will be appreciated thatt4 and t3 occur instantaneously but have been written out as discretesteps for ease of understanding the inventive circuitry. Oncemicroprocessor 80 reverses the voltages at step t3, it is free to turnitself off until the voltage at line (b) drops to a low voltageindicating that electrode pair 142 is no longer immersed in water.

When water level decreases at a later arbitrary time t5, electrode pair142 contacts air and the logical switch defined by electrode pair 142 isonce again in the open state. The opening of switch 142 means that R₂becomes large. Therefore V_(OUT), decreases meaning that there is avoltage drop at (b). The voltage drop at (b) causes microprocessor 80 towake up from its idle state and to note the change in water level belowelectrode pair 142.

Immediately after time t5, microprocessor 80 again reverses inputvoltages of leads (a) and (c), such that lead (a) becomes low and lead(c) becomes high. Thus, the voltage at lead (b) is once again defined bythe equation:

$V_{OUT} = {V_{IN}\left\lbrack \frac{R_{2}}{R_{1} + R_{2}} \right\rbrack}$As such, at time t7, the voltage at terminal (b) is returned to the highstate because R₂ is large. Further, at time t7, the microprocessor againreturns to the idle state. At time t7, switch 142, microprocessor 80 andleads (a), (b) and (c) are in the same state that they were in at timet0, with microprocessor waiting in an low power consumption idle statethat will only be disturbed by a voltage drop at lead (b). At some latertime t8, water level increases again such that it immerses leads 142,and the cycle described for times t0–t7 starts again.

The exemplary circuit shown and described in FIGS. 8 and 9 relates toone electrode pair 142 in the array of electrode pairs 142 of sensor140. One of skill in the art will appreciate that, in a preferredembodiment, each electrode pair is connected to a separate voltagedivider circuit such that changes in the state of every electrode in thearray can be monitored by processor 80. This approach is advantageousfrom a power efficiency standpoint because, while microprocessor 80 isconstantly ready to respond to changes in water level, it remains idleuntil such a change occurs. Moreover, even when a change occurs,microprocessor 80 effectively ignores all electrodes 142 except thosethat are directly affected by the change in water level at any giventime. Another advantage of the exemplary circuitry is that very littlecurrent is run through the detection circuitry. The instant a voltagedrop occurs at (b) indicating that a current is running through 142-1,the voltages at (a) and (c) are reversed thereby stopping the current.This has the beneficial effect of prolonging battery life and reducingcorrosion at leads 142.

One skilled in the art will appreciate that the capacitance principlesdiscussed above with respect to FIG. 4B can be applied to configuredetection circuit 170 such that circuits 172 detect changes incapacitance at electrode pairs 142 with increases or decreases in waterlevel. Such capacitance circuits need only detect whether capacitance ishigh or low at a given sensor. For example, the uppermost sensor with ahigh capacitance indicates water level. Optionally, a power-efficientcircuit such as that described above could be configured to detectchanges in capacitance using capacitance principles described herein.

Alternative Water Level Sensors

FIGS. 10–12 depict alternative embodiments of water level sensor 40.Referring to FIG. 10, a water level sensor 200 comprises a substrate 46having a long vertical electrode 210 juxtaposed to a vertical array ofsmaller electrodes 212-N. Electrode 210 is similar to one of electrodes42 a or 42 b of FIG. 2A, while each electrode in electrodes 212-N issimilar to an electrode 142 a or 142 b of FIG. 6A. Electrodes 210 and212 are attached to or imbedded within substrate 46, and extend from thesurface of substrate 46 such that any water in cavity 19 of container 10contacts the electrodes. In this embodiment, sensor 200 can functionessentially as sensor 140 described above with respect to FIGS. 6–9,with electrode 210 acting as a common electrode forming an electrodepair with each of electrodes 212. Each electrode 210 and 212 isconnected by a lead to detection circuitry such as detection circuit170. Detection circuit 170 can be configured to detect changes inresistance or capacitance at each electrode pair as described above. Theadvantage of sensor 200 (FIG. 10) over sensor 140 (FIG. 6A) is thatsensor 200 is cheaper to build because it contains less discrete partsand less wiring.

In another embodiment, water level sensor 300 of FIG. 11 includes commonelectrode 210 attached to substrate 46. However, instead of a verticalarray of essentially identical short electrodes 212 as in sensor 200,sensor 300 includes a parallel array of vertically-oriented electrodes312 of varying length. Water level sensor 300 relies on the principlethat the resistance between electrode 210 and an electrode 312 willmeasurably decrease as soon as water immerses the tip of an electrode312. Thus, an array of electrodes 312, with each electrode 312 have adifferent predetermined length, can be used to determine water levelusing the resistance principles discussed above.

In another embodiment, water level sensor 400 of FIG. 12 includesparallel pairs of electrodes 442, with each electrode pair 442comprising a first electrode 442 a and a second electrode 442 b. As withother sensors described herein, the electrodes are mounted on, attachedto, or imbedded into substrate 46 such that they extend from thesubstrate and contact either air or water. As with sensor 300, the topedge of each electrode pair is aligned near the top of sensor 400. Eachelectrode in a pair, e.g., 442 a-1 and 442 b-1, has the same length.However, in preferred embodiments, each pair of electrodes 442 has aunique length in sensor 400, as illustrated in FIG. 12. For example,electrodes 442 a-1 and 442 b-1 span only a short vertical distance fromthe top of sensor 400, while electrodes 442 a-N and 442 b-N spanessentially the entire vertical length of sensor 400. Electrode pairsbetween 442-1 and 442-N are of intermediate lengths, such that eachelectrode pair corresponds to a particular water depth. Each electrodeis connected by a respective lead 441 to detection circuitry asdescribed above. In use, electrode 400 functions essentially the same aselectrode 140 (FIG. 6B) described above.

It shall be noted that the shapes and configurations of electrodes shownand described herein are only examples and are not meant to be limiting.Other configurations, materials, and methods of manufacture can be usedwithout departing from the scope of the present invention.

Alternative and Additional Features of the Inventive Filtered WaterContainers

FIG. 13 illustrates container 500, which represents an alternativeembodiment of the present invention. Container 500 is essentially thesame as container 10 (FIG. 1), except that it includes additionaloptional features to improve accuracy of determinations such ascumulative water usage and filter cartridge status by allowing manual orautomatic inactivation of water level detection and monitoring system 50during certain “non-functional” periods or events such as cleaning andtilting of the container.

Body 12, lid 14, hopper 24 and filter cartridge 22 of container 500 areall essentially the same as described with respect to FIG. 1. The basiccomponents of water level detection and monitoring system 50 are alsoessentially the same, including water level sensor 40, electroniccontrol system 52 (including detection circuit and control unit whichare not shown), and display 60. In addition to these components,however, container 500 optionally includes one or more switches 510 and520 that are electronically connected to electronic control system 52.In some embodiments, container 500 contains a switch (not shown) betweenhopper 24 and body 12. When hopper 24 is removed from body 12, thisswitch is in a first state, indicating that filtered water container 500is in nonfunctional state and when the hopper is fitted within body 12as illustrated in FIG. 13, this switch is in a second state, indicatingfiltered water container 500 is in a functional state.

Container 500 also optionally includes one or more additional waterlevel sensors 530 and 540 that are electrically connected by one or morewires (e.g., wire 554) to electronic control system 52, and work inconjunction with water level sensor 40. In such embodiments, each sensor40, 530, and 540 may be any of sensors 40 of FIGS. 2A and 2B, sensor 140of FIGS. 6A and 6B, sensor 200 of FIG. 10, sensor 300 of FIG. 11, sensor400 or FIG. 12. In such embodiments, microprocessor uses electrode pairsfrom any combination of sensors 40, 530, and 540 to determine the waterlevel 27 of container 500. Furthermore, the use of multiple sensors 40,530, and/or 540 in a configuration such as that illustrated in FIG. 13provide additional advantages that will be described in detail below.

Switches for Determining Non-Functional Periods of Use

Switches 510 and 520 can be electromechanical, electromagnetic, opticalor otherwise, and may be operated manually, e.g., by a user, orautomatically, e.g., by the removal or misplacement of some component ofcontainer 500. For example, switch 510 is shown as a manual mechanicalslide switch that may be toggled by a user to turn off, suspend, orreset operation of water level detection and monitoring system 50. Forexample, it may be desirable to suspend operation of system 50 in orderto differentiate the change of water level in the lower portion of thecontainer during normal consumption/filtration from non-functionalperiods such as cleaning of the container with water. Optionally,turning off switch 510 could cause system 50 to reset, such as when anew filter cartridge 22 is installed or when a user wishes to resetcumulative water usage or consumption calculations.

Optional lid switch 520 is depicted as an automatic button or springswitch that is activated when lid 14 is removed. As with manual switch510, lid switch 520 is electrically connected to electronic controlsystem 52 such that it can be used to suspend operation of water leveldetection and monitoring system 50, for example by sending a signal tomicroprocessor 80 or by causing an interruption in the detectioncircuit. In such instances, operation of system 50 resumes when lid isre-attached in proper fashion to body 12. Additional or alternativeswitches, whether electromechanical, electromagnetic, optical orotherwise, can be used to detect proper contact between hopper 24 andbody 12, lid 14 and hopper 24, or any combination thereof. The propercontact between these parts signals the control system 52 todifferentiate the status of the water container 500 between periods ofnormal consumption/filtration and nonfunctional periods (e.g. whilecontainer 500 is being cleaned).

Alternatively, or in combination with the use of switches, controlsystem 52 can be programmed to differentiate a change in water level 27in normal consumption/filtration from non-functional changes in waterlevel 27 by computing and analyzing the rate of water level change. Suchnon-functional changes in water level 27 include its change duringfilling and emptying container 500 with water during cleaning, duringpouring of filtered water out of the lower portion of container 500, andmovement of the water level 27 during transportation of container 500.Thus, sampling of the water level 27 during these non-functional changesin water level 27 will cause inaccuracy in computing information such asfiltered water consumption and usage of the removable filter cartridge22. The rate of water filtration through a cartridge 22 with a knownamount and chemistry of its filter medium can be experimentallydetermined. Although the filtration rate may decrease with usage,particularly if the water contains particulate matters, the variation inthe filtration rate remains relatively constant throughout the life of acartridge. Since non-functional changes in water level 27 are mostlikely faster than its change during filtration, the microprocessor incontrol unit 52 can ignore non-functional changes in water level 27 whenmonitoring water consumption or water filtration since the lastcartridge 22 replacement.

Bubble Level Switch

In an alternative embodiment of the invention, a bubble level switch 600as shown in FIG. 14, is used to avoid erroneous detection in the changeof water level that may occur when the water container is stored in atilted position or else due to non-functional changes of water level.Bubble level sensor 600 is comprised of an enclosure 610 containing twoelectrodes 630 and 640 separated by a defined amount of liquid 620 thatconducts electricity. The amount of liquid 620 in enclosure 610 is lessthat the volume of enclosure 610 between the two electrodes 630 and 640,such that a bubble of air or other gas is present between electrodes 630and 640. Electrodes 630 and 640 are connected externally by leads 635and 645, respectively, to detection circuit 70 or 170 and microprocessor80 as shown in FIGS. 4 and 7. The current pathway between electrodes 630and 640 within enclosure 610 is established when the liquid 620 level isessentially horizontal. When level sensor 600 is tilted, bubble 620moves toward the higher electrode 630 or 640 and causes a change orinterruption in the resistance, capacitance or other measurable propertybetween electrodes 630 and 640, which is then detected by control unit80.

The ability of this embodiment of the invention to detect a stationaryhorizontal water level allows the control unit 80 to distinguish andfactor into its calculations the changes in water level 27 during normalconsumption/filtration from that due to tilted water container positionsor non-functional changes. A further advantage of being able to detect astationary horizontal water level 27 is the simplicity in programmingthe control unit 80 to record, monitor and analyze water level 27 onlyif the detection circuitry detects a stationary horizontal water level.Yet another related advantage provided by the method is obviating theneed for control unit 80 to store or else analyze data such as the rateof change in water level and the filtration rate of a given cartridge22. In a preferred embodiment of the invention, the control unit 80 cangenerate an audible and/or visual signal to alert the user to uprightthe storage position of container 500 for proper monitoring of waterconsumption and water filtration, or else for the prevention of tippingover of container 500.

Multiple Detection Sensors

Referring again to FIG. 13, the ability of the control unit to monitorwater level change during normal consumption/filtration is enhanced bythe inclusion of one or more additional detection sensors 530 and 540located along the inner wall of the lower portion 19 of filtered watercontainer 500, and are positioned as far apart as possible. As discussedabove with respect to sensor 40 and 140, the water level at eachdetector strip is detected, recorded, monitored and analyzed by theelectronic control system 52, including detection circuit 70 and controlunit 80 as described above. Using multiple detection sensors 40, 530 and540, the detection circuit and the control unit together are capable ofdetecting a stationary horizontal water level with container 500 beingplaced on a relatively horizontal surface during normalconsumption/filtration. In contrast, with a single detector strip 40, anerroneous detection in the change of water level can occur when thefiltered water container 500 is stored in a tilted position or else dueto non-functional changes of water level.

In another embodiment of the invention utilizing multiple detectionsensors 40, 530 and 540, the filtered water level 27 can be measured andmonitored conveniently even if the filtered water container isperpetually in motion or perpetually titled, such as its use in anautomobile or on an airplane. The filtered water level 27, whetherstationary or not, can be viewed three-dimensionally as a plane thattransverses the water surface. With at least three detector strips 40,530 and 540, the position of the water surface 27 plane in space isdetected instantaneously. Hence, the volume of filtered water in thelower portion 19 of filtered water container 500 can be computed even ifthe water level is not stationary.

The illustrative descriptions of the application of the principles ofthe present invention are to enable any person skilled in the art tomake or use the disclosed invention. All references cited herein areincorporated by reference herein in their entirety. These descriptionsare susceptible to numerous modifications and alternative arrangementsby those skilled in the art. Such modifications and alternativearrangements are not intended to be outside the scope of the presentinvention. The appended claims are intended to cover such modificationsand arrangements. Thus, the present invention should not be limited tothe described illustrative embodiments but, instead, is to be accordedthe broadest scope consistent with the principles and novel featuresdisclosed herein.

1. A water level monitoring system for determining an amount of wateradded to and/or consumed from a filtered water container comprising: adetection sensor comprising an electrode pair, the electrode paircomprising a first electrode and a second electrode spaced sufficientlyapart from each other so that an electrical property associated with thefirst and second electrodes that changes with changes in a water levelin said filtered water container can be detected; a detection circuitconnected to the electrode pair in the detection sensor and capable ofgenerating signals based on the electrical property associated with theelectrode pair; and a control unit connected to the detection circuitand capable of receiving signals from the detection circuit, wherein thecontrol unit determines changes in the water level in said filteredwater container from the signals received from the detection circuit andthereby determines said amount of filtered water added to and/orconsumed from said filtered water container over a period of time inwhich water is added to and consumed from the container.
 2. The systemof claim 1 wherein the electrical property associated with the firstelectrode and the second electrode is one or more of: a resistanceacross said first electrode and said second electrode, a change in acapacitance between said first electrode and said second electrode, avoltage across said first electrode and said second electrode, and acurrent across said first electrode and said second electrode.
 3. Thesystem of claim 1, further comprising a switch that is in electricalcommunication with said control unit wherein, when said switch is in afirst state, said control unit determines that said filtered watercontainer is in a nonfunctional state, and when said switch is in asecond state, said control unit determines that said filtered watercontainer is in a functional state, and wherein said control unitdetermines changes in water level occurring when said filtered watercontainer is in said functional state, and said control unit does notdetermine changes in water level occurring when said filtered watercontainer is in said nonfunctional state.
 4. The system of claim 3wherein said switch is toggled between said first state and said secondstate by a user.
 5. The system of claim 3 wherein said switch ispositioned within said filtered water container so that said switch isin said first state when a lid of the filtered water container is open,and said switch is in said second state when said lid is closed.
 6. Thesystem of claim 3 wherein said switch is a bubble level switch thatcomprises a first bubble sensor electrode and a second bubble sensorelectrode in an enclosure trapping (i) a fluid and (ii) a bubble;wherein said bubble sensor electrode is in said first state when saidbubble contacts one of said first bubble sensor electrode and saidsecond bubble sensor electrode; and said bubble sensor electrode is insaid second state when said bubble does not contact said first bubblesensor electrode or said second bubble sensor electrode.
 7. The systemof claim 1 wherein: said control unit determines that said filteredwater container is in a functional state when a rate of change in awater level in said filtered water tank is below a predetermined rate;said control unit determines that said filtered water container is in anonfunctional state when a rate of change in a water level in saidfiltered water tank is above a predetermined rate; said control unitdetermines changes in water level occurring when said filtered watercontainer is in said functional state, and said control unit does notdetermine changes in water level occurring when said filtered watercontainer is in said nonfunctional state.
 8. The system of claim 3wherein the filtered water container is fitted with a hopper that holdsunfiltered water and wherein the hopper is fitted at its base with areplaceable filter cartridge so that water is filtered by drainingthrough the filter cartridge into a lower portion of the water filtercontainer; and wherein said switch is positioned within said filteredwater container so that said switch is in said first state when thehopper is removed from said filtered water container, and said switch isin said second state when said hopper is fitted within said filteredwater container.
 9. The system of claim 1 wherein the filtered watercontainer is fitted with a hopper that holds unfiltered water andwherein the hopper is fitted at its base with a replaceable filtercartridge so that water is filtered by draining through the filtercartridge into a lower portion of the water filter container.
 10. Thesystem of claim 1, further comprising a display in electricalcommunication with said control unit, wherein the control unit iscapable of causing the display to display information derived from thechanges in water level.
 11. The system of claim 1, further comprising adisplay in electrical communication with said control unit, wherein thecontrol unit is capable of causing the display to display one or more ofa water level of said filtered water level container, a status of awater filter that is disposed within said filtered water container, adetermination of whether said filtered water container is in afunctional state, a determination of whether said filtered watercontainer is in a nonfunctional state, a time elapsed or an amount offiltered water consumed since a last filter cartridge change, a currenttime, a warning of overfilling, or a reminder to refill.
 12. The systemof claim 1 wherein said detection sensor further comprises one or moreadditional electrode pairs, each electrode pair comprising a firstelectrode and a second electrode spaced sufficiently apart from eachother so that an electrical property associated with the first andsecond electrodes that changes with changes in the water level can bedetected, said detection circuit further comprises one or moreadditional circuits corresponding to the one or more additionalelectrode pairs, wherein each circuit in the detection circuit isconnected to its corresponding electrode pair in the detection sensorand is capable of generating a signal based on the electrical propertyof its corresponding electrode pair; and said control unit is capable ofreceiving the signals from the one or more circuits in the detectioncircuit and determines changes in the water level in said filtered watercontainer from the signals received from the one or more circuits in thedetection circuit and thereby determines an amount of filtered waterconsumption.
 13. The system of claim 12 wherein the electrical propertyassociated with said first electrode and said second electrode in saidone or more additional electrode pairs is one or more of: a resistanceacross said first electrode and said second electrode, a capacitancebetween said first electrode and said second electrode, a voltage acrosssaid first electrode and said second electrode, or a current across saidfirst electrode and said second electrode.
 14. The system of claim 12wherein said control unit determines changes in filtered water levelbased on the electrical properties associated with at least twoelectrode pairs.
 15. The system of claim 1, wherein the control unitmonitors a status of a water filter that is in said filtered watercontainer based on signals received from said detection circuit.
 16. Awater level monitoring system for determining an amount of water addedto and/or consumed from a filtered water container comprising: adetection sensor extended along a length of the filtered watercontainer, the detection sensor comprising a plurality of electrodepairs, each respective electrode pair in the plurality of electrodepairs comprising a first electrode and a second electrode spacedsufficiently far apart from each other in the respective electrode pairso that an electrical property associated with the first and secondelectrodes that changes with changes in the water level can be detected;a detection circuit in electrical communication with the plurality ofelectrode pairs in the detection sensor, the detection circuit capableof generating signals based on the respective electrical properties ofthe first and second electrodes in the plurality of electrode pairs; anda control unit in electrical communication with the detection circuit,wherein the control unit determines changes in the water level in saidfiltered water container from the signals received from the detectioncircuit and thereby determines the amount of water added to and/orconsumed from said filtered water container over a period of time inwhich water is added to and consumed from the container.
 17. The systemof claim 16 wherein the electrical property associated with one or moreof said first and second electrodes in the plurality of electrode pairsis one or more of: a resistance across said first electrode and saidsecond electrode, a capacitance between said first electrode and saidsecond electrode, a voltage across said first electrode and said secondelectrode, and a current across said first electrode and said secondelectrode.
 18. The system of claim 16 wherein said plurality ofelectrode pairs comprises between 2 electrode pairs and 10 electrodepairs.
 19. The system of claim 16 wherein said plurality of electrodepairs comprises more than 10 electrode pairs.
 20. The system of claim 16further comprising a first lead (a), a second lead (b) and a third lead(c), wherein said first lead (a) is in electrical communication withsaid first electrode of one of the electrode pairs in said plurality ofelectrodes; said second lead (b) is in electrical communication withsaid second electrode of the one electrode pair in said plurality ofelectrodes; and said third lead (c) and said second lead (b) are inelectrical communication across a resistor; and wherein said controlunit sets said third lead (c) to one of a high or low voltage and saidfirst lead to the other of the high or low voltage, thereby producing ahigh voltage on second lead (b), and reverses the voltage states of thefirst and third leads each time a voltage drop is detected at saidsecond lead (b).
 21. The system of claim 20 wherein said control unitswitches to a low power consumption idle state when said second lead (b)is in a high voltage state.
 22. The system of claim 20 wherein saidcontrol unit switches to a high power consumption state when said secondlead (b) drops from a high voltage state to a low voltage state.
 23. Thesystem of claim 16, further comprising a switch that is in electricalcommunication with said control unit wherein, when said switch is in afirst state, said control unit determines that said filtered watercontainer is in a nonfunctional state, and when said switch is in asecond state, said control unit determines that said filtered watercontainer is in a functional state, and wherein said control unitdetermines changes in water level occurring when said filtered watercontainer is in said functional state, and said control unit does notdetermine changes in water level occurring when said filtered watercontainer is in said nonfunctional state.
 24. The system of claim 23wherein said switch is toggled between said first state and said secondstate by a user.
 25. The system of claim 23 wherein said switch ispositioned within said filtered water container so that said switch isin said first state when a lid of the filtered water container is open,and said switch is in said second state when said lid is closed.
 26. Thesystem of claim 23 wherein said switch is a bubble level switch thatcomprises a first bubble sensor electrode and a second bubble sensorelectrode in an enclosure trapping (i) a fluid and (ii) a bubble;wherein said bubble sensor electrode is in said first state when saidbubble contacts one of said first bubble sensor electrode and saidsecond bubble sensor electrode; and said bubble sensor electrode is insaid second state when said bubble does not contact said first bubblesensor electrode or said second bubble sensor electrode.
 27. The systemof claim 16 wherein: said control unit determines that said filteredwater container is in a functional state when a rate of change in awater level in said filtered water tank is below a predetermined rate;said control unit determines that said filtered water container is in anonfunctional state when a rate of change in a water level in saidfiltered water tank is above a predetermined rate; said control unitdetermines changes in water level occurring when said filtered watercontainer is in said functional state, and said control unit does notdetermine changes in water level occurring when said filtered watercontainer is in said nonfunctional state.
 28. The system of claim 23wherein the filtered water container is fitted with a hopper that holdsunfiltered water and wherein the hopper is fitted at its base with areplaceable filter cartridge so that water is filtered by drainingthrough the filter cartridge into a lower portion of the water filtercontainer; and wherein said switch is positioned within said filteredwater container so that said switch is in said first state when thehopper is removed from said filtered water container, and said switch isin said second state when the hopper is fitted within said filteredwater container.
 29. The system of claim 16 wherein the filtered watercontainer is fitted with a hopper that holds unfiltered water andwherein the hopper is fitted at its base with a replaceable filtercartridge so that water is filtered by draining through the filtercartridge into a lower portion of the water filter container.
 30. Thesystem of claim 16, further comprising a display in electricalcommunication with said control unit, wherein the control unit iscapable of causing the display to display information derived fromchanges in the current water level.
 31. The system of claim 16, furthercomprising a display in electrical communication with said control unit,wherein the control unit is capable of causing the display to displayone or more of a water level of said filtered water level container, astatus of a water filter that is disposed within said filtered watercontainer, a determination of whether said filtered water container isin a functional state, a determination of whether said filtered watercontainer is in a nonfunctional state, a time elapsed or an amount offiltered water consumed since a last filter cartridge change, a currenttime, a warning of overfilling, and a reminder to refill.
 32. The systemof claim 16 further comprising one or more additional detection sensors,each extending along a length of the filtered water container, andwherein each additional detection sensor comprises a plurality ofelectrode pairs, each electrode pair in the plurality of electrode pairscomprising a first electrode and a second electrode, each in electricalcommunication with said detection circuit.
 33. The system of claim 32wherein the control unit determines changes in the filtered water levelbased on the electrical properties associated with at least twoelectrode pairs.
 34. The system of claim 16 wherein a single commonelectrode represents the first electrode in each electrode pair in saidplurality of electrode pairs.
 35. The system of claim 16 wherein eachsecond electrode in all or a portion of the plurality of electrode pairshas a unique length.
 36. The system of claim 16 wherein a single commonelectrode represents the first electrode in each electrode pair in saidplurality of electrode pairs, each second electrode in all or a portionof the plurality of electrode pairs has a unique length; and a length ofeach second electrode in all or a portion of the plurality of electrodepairs is used by said control unit to determine a water level in thefiltered water container.
 37. The system of claim 16 wherein a length ofall or a portion of the electrode pairs in the plurality of electrodepairs is different, and a length of each electrode pair in all or aportion of the plurality of electrode pairs is used by said control unitto determine a water level in the filtered water container.
 38. A methodof measuring changes in a water level in a filtered water containercomprising the steps of: generating a signal based on an electricalproperty associated with a first electrode and a second electrode in anelectrode pair, said electrical property changing with changes in thewater level in said filtered water container; and determining changes inthe water level in said filtered water container from the generatedsignals; and determining an amount of filtered water consumption fromthe changes in the water level over a period of time in which water isadded to and consumed from the container.
 39. The method of claim 38wherein the electrical property associated with said first electrode andsaid second electrode is one or more of: a resistance across said firstelectrode and said second electrode, a change in a capacitance betweensaid first electrode and said second electrode, a voltage across saidfirst electrode and said second electrode, and a current across saidfirst electrode and said second electrode.
 40. The method of claim 38,the method further comprising the step of determining a status of awater filter in said filtered water container based on the changes inthe water level.
 41. The method of claim 38, wherein the step ofgenerating generates signals from a plurality of electrode pairs andwherein a first lead is in electrical communication with said firstelectrode of one of the electrode pairs in said plurality of electrodepairs; a second lead is in electrical communication with said secondelectrode of the one electrode pair in said plurality of electrodepairs; and a third lead and the second lead are in electricalcommunication across a resistor; and further comprising the steps of:setting the third lead to one of a high or low voltage and said firstlead to the other of the high or low voltage, thereby producing a highvoltage on the second lead; and reversing the voltage states of thefirst and third lead each time a voltage drop is detected at said secondlead.
 42. A method of measuring a water level of a filtered watercontainer comprising: generating signals based on electrical propertiesof a plurality of electrode pairs, the electrical property of eachelectrode pair in the plurality of electrode pairs changing with changesin the water level in said filtered water container; and determiningchanges in the water level in said filtered water container from thegenerated signals; and determining an amount of filtered waterconsumption from the changes in the water level over a period of time inwhich water is added to and consumed from the container.
 43. The methodof claim 42 wherein the electrical property associated with said firstelectrode and said second electrode is one or more of: a resistanceacross said first electrode and said second electrode, a change in acapacitance between said first electrode and said second electrode, avoltage across said first electrode and said second electrode, and acurrent across said first electrode and said second electrode.
 44. Themethod of claim 42, the method further comprising the step of:determining a status of a water filter in said filtered water containerbased on the changes in the water level.